a. Field of the invention
The present invention relates to a focal plane shutter and, more particularly, to a flash synchronizing device pertaining to said type of shutter for accurately synchronizing lighting of the flash bulb and opening of the shutter.
B. Description of the prior art
For focal plane shutters, it is generally required, in order to synchronize lighting of the flash bulb and opening of the shutter, to change the time lag between the instant of closing of the flash circuit and instant of starting of the shutter opening motion in proportion to the shutter speed by taking the lighting characteristic of the flash bulb to be used into consideration. To satisfy the above requirement, the known focal plane shutters are arranged as follows. That is, a pair of switch levers which are actuated by a cam or pin is provided for closing the flash circuit and the mutual distance of said pair of switch levers is changed according to the shutter speed to be set. Alternately, a C-R delay circuit is provided for closing the flash circuit and the time constant of said delay circuit is changed according to the shutter speed. Said known types of focal plane shutters, however, have disadvantages as described below. That is, it is impossible to obtain the accurate time lag suitable for the set shutter speed, operation is unstable, or the device itself becomes comparatively complicated.